Diabetic Kidney Disease in the United States

In the developed world, diabetic kidney disease (DKD) is the leading cause of chronic kidney disease. It is estimated that 40% of individuals with diabetes develop DKD, manifested as albuminuria, impaired glomerular filtration rate (GFR), or both. Patients with even mild degrees of these conditions are at increased risk for cardiovascular disease and death as well as higher healthcare costs. DKD accounts for approximately half of all incident cases of end-stage renal disease (ESRD) in the United States. In 2008, Medicare spending associated with the US ESRD program was $26.8 billion. From 1998 to 2006, the prevalence of diabetes among US adults ≥20 years of age increased from 7.4% to 9.6%. During the same period, clinical trials found that lowering blood glucose levels reduced the risk of developing albuminuria and that inhibitors of the renin-angiotensin-aldosterone system (RAAS) reduced albuminuria and the risk of progressive disease in GFR, leading to changes in standards of care. Over time, the prevalence of DKD may increase due to growth in the diabetes population or decrease due to implementation of advanced diabetes therapies, according to researchers, who recently conducted a study to examine trends in the prevalence of DKD in the United States over the past 20 years and examine changes in disease manifestations among individuals with diabetes. Results of the study were reported in the Journal of the American Medical Association [2011;305(24):2532-2539]. The main outcome measure was DKD. In the study, DKD was defined as diabetes with albuminuria (ratio of urine albumin to creatinine ≥40 mg/g), impaired glomerular filtration rate (<60 mL/min/1.73 m2 estimated using the Chronic Kidney Disease Epidemiology Collaboration formula), or both. Prevalence of albuminuria was adjusted to estimate persistent albuminuria. Participants were identified through the Third National Health and Nutrition Examination Survey (NHANES III) from 1988-1994 (n=15,073), NHANES 1999-2004 (n=13,045), and NHANES 2005-2008 (n=9588). Of those, there were 1431, 1443, and 1280, respectively, who had diabetes. The weighted national prevalence of diabetes was 6.0% in NHANES III, 7.8% in NHANES 1999-2004, and 9.4% in NHANES 2005-2008. In the period 1988-1994, the prevalence of DKD in the US population was 2.2%; in 1999-2004, the prevalence was 2.8%, and in 2005-2008 the prevalence was 3.3%. The demographically adjusted increase in DKD prevalence was 18% from 1988-1994 to 1999-2004 and 34% from 1998-1994 to 2005-2008 (P=.03 for trend). Among individuals with diabetes, the proportion of those taking glucose-lowering medications increased from 56.2% in NHANES III to 74.2% in NHANES 2005-2008; mean hemoglobin A1c values decreased from 8.1% to 7.3% (P<.001 for trend). Use of RAAS inhibitors increased from 11.2% to 40.6%; mean systolic and diastolic blood pressure decreased from 136/76 mm Hg to 131/69 mm Hg (P<.001 for trend for each comparison). Use of lipid-lowering medications (primarily statins) increased from 8.9% to 50.2%; mean low-density lipoprotein cholesterol levels decreased from 137 mg/dL to 105 mg/dL (P<.001 for trend for each comparison). The prevalence of impaired GFR (with or without albuminuria) increased from 14.9% in 1988-1994 to 16.7% in 1999-2004 to 17.7% in 2005-2008, demographically adjusted increases in prevalence of 21% from 1999-2004 versus 1988-1994 and 29% from 2005-2008 versus 1988-1994 (P=.03 for trend). The mean estimated GFR decreased by 3.9 mL/min/1.73 m2 from 1988-1994 to 1999-2004 and from 1999-2004 to 2005-2008. In summary, the researchers commented, “Prevalence of DKD in the United States increased from 1988 to 2008 in proportion to the prevalence of diabetes. Among persons with diabetes, prevalence of DKD was stable despite increased use of glucose-lowering medications and renin-angiotensin-aldosterone system inhibitors.”